Field collections extended the range of Aedes hendersoni Cockerell east into Indiana, Michigan, and Ohio. One field-collected larva had characters of both A. hendersoni and A. triseriatus (Say) and was very similar to laboratory produced F1 hybrids. A. hendersoni was successfully colonized, and hybridized to A. triseriatus in the laboratory by the forced-copulation technique. In crosses of A. hendersoni females to A. triseriatus males, F1 females and males were fertile. However, in the reciprocal cross the F1 females were fertile, but the males had abnormal genitalia and could not mate. Backcrosses and the F2 cross showed that several characters, which are used for specific separation of larvae of A. hendersoni and A. triseriatus, behave as if they were controlled by single genes. These characters segregated in simple Mendelian ratios and may be useful in studies of the genetics of the two species.